Conventionally, capping machines of the type in question are equipped with at least one rotary conveyor mounted to the central shaft of the carousel together with the capping units, in such a way as to rotate as one with these same units about the main axis of the machine.
The aforementioned rotary conveyor lies beneath the carousel drum, by which the capping units are carried during operation, and establishes a substantially circular trajectory or path extending between a container infeed station and a container outfeed station.
In particular, containers are taken up from the infeed station by the rotary conveyor and carried to the outfeed station, where they will be released after undergoing one or more operations performed by the capping units, that is to say after being capped and sealed.
To this end, the prior art embraces various types of rotary conveyors.
A first type of conveyor is equipped with a plurality of recesses distributed circumferentially about the main axis of the machine, each designed to accommodate a single container for processing, at least in part. The conveyor also presents one or more lateral restraints associated with the recesses, serving to guide the containers along the circular path and around the main axis of the machine. The containers advance with their side walls sliding against the lateral restraints and their bases resting on a common platform.
The prior art embraces other types of conveyor making no use of a fixed lateral restraint, but rather, furnished with a suitable system of pressure belts by which the containers being capped are held forcibly against the respective recesses. The recesses are faced with a material having a high coefficient of friction, so that the action of the belts and the grip afforded by the facings of the recesses will combine more effectively to counteract the rotational forces induced by the capping units.
Finally, the prior art includes conveyors with recesses created by the jaws of respective gripper mechanisms. The jaws can be spread in order to admit the respective container, and thereupon closed by suitable spring means. Thus, the containers are retained and carried along the circumferential conveying path with no need for a lateral restraint of any description.
Whilst the conventional conveyors described above are able to transfer containers efficiently from an infeed station to an outfeed station of a machine by which the selfsame containers are processed, the systems adopted are not without certain drawbacks and might be improved in various ways, mainly as regards counteracting the rotational movements that tend to be induced in the containers in the course of their being handled, for example when caps are fitted, and maintaining the structural integrity of the selfsame containers during their passage from the infeed to the outfeed station.
The applicant finds, in particular, that because the containers are not restrained satisfactorily during the capping operation, there is the risk that a single container can rotate together with the cap being applied, and with the respective capping head. In other words, a container can be forced into rotation by the action of the respective capping unit, with the result that the closure may be insufficiently secure, and the container itself may emerge with scratches or other surface damage caused by the body rubbing against the recesses, the restraints, the belts or the gripper jaws.
It will be appreciated also, in the case of conveyors equipped with complex pressure belt systems, that these systems are difficult to clean or wash and have a high maintenance requirement in terms of the need for replacement and adjustment of the various parts subject to wear, namely the belts and the relative mechanical drive transmission components.
Moreover, a change in the size or style of container handled by the capping machine involves lengthy interruptions to the production cycle, since the changeover dictates replacement both of the parts creating the recesses by which the containers are accommodated, and of the support element or disc carrying the recesses, which normally will be keyed onto a shaft of the machine.